Proton Transfer Reaction Mass Spectrometry: Applications in the Life Sciences

Tracing Hidden Herbivores: Time-Resolved Non-Invasive Analysis of Belowground Volatiles by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)

“…Previous GC analyses have not detected methanethiol, which might originate from the compound selectivity of the adsorbents that have been used for collection. Interestingly, we also found a considerable increase in m/z = 60, which is related to glucosinolate breakdown products (Crespo, 2012 ). This is a typical characteristic of members of the Brassicaceae after tissue damage.…”

“…The resulting mass scan (Fig. 3 ) shows that the intensities of several molecular masses are enhanced in root fly infested B. rapa roots, the identities of which were confirmed by Crespo ( 2012 ) by additional GC-MS analysis and PTR-MS measurements of authentic standards. The induced intensities were detected in several structurally related sulfides, some of which have been shown to be induced in more than one Brassica species after root fly feeding, and which are exploited as cues by parasitoids and predators (Ferry et al, 2007 ; Soler et al, 2007 ).…”

“…PTR-MS of plant VOCs requires the amount of these ions to be reduced, because they transfer their charge to most VOCs without adding a proton, which complicates the identification of compounds. However, higher levels of NO + and O 2 + ions may also be beneficial for detecting specific compounds, such as sulfur-containing glucosinolate breakdown products (Crespo, 2012 ).…”

“…2 ). The two parts of the cuvette were sealed together with Terostat IX (Henkel, UK), a solvent–free, rubber-based sealant (Crespo, 2012 ) to prevent ambient air from entering. During measurements, an excess flow of hydrocarbon-free air into the cuvette was maintained, similar to a typical dynamic headspace collection setup (Tholl et al, 2006 ).…”